1. Technical Field
The present invention relates to a detection device, a printer, and a control method for a detection device, and relates more particularly to technology for reducing power consumption.
2. Related Art
Some printers and other small information devices operate using DC power supplied from an externally connected power supply device. Demand has also increased for devices that suppress supplying DC power to relatively high power consumption components, such as internal circuits including the CPU (microprocessor), during idle time in order to reduce power consumption. This idle time (waiting time) is a period when the power switch of the information device is on but the information device is not used for an extended period of time and the primary function of the information device is not utilized.
Some countries also have regulations requiring the use of environmental design (such as “Design for Environment” (DfE) or “EcoDesign”) principles in energy-using products. Some countries also require suppression of power consumption to a specified level or below when in the off -mode (an operating state in which the information device is connected to a commercial power supply but no information device functions are being used).
System-on-chip (SoC) devices that integrate a group of functions required for a particular application on a single semiconductor chip are also known from the literature.
However, because SoC devices consume a lot of power even when idle, energy efficiency is achieved by entering a sleep mode or other energy conservation mode.
Depending upon where the printer is installed, ambient light such as sunlight entering the printer from the paper insertion opening or the paper exit maybe incident to the paper detector used in conventional printers. This ambient light can be detected by the photodetector of the paper detector and result in detection errors.
This can result in falsely determining that paper is present even though there is no recording paper, or falsely determining that there is no paper even though recording paper is present.
To solve this problem, Japanese Unexamined Patent Appl. Pub. JP-A-2002-068529 teaches technology for cancelling the effect of ambient light so that recording paper can be detected without being affected by ambient light even under conditions prone to detection errors due to such ambient light.
However, reducing power consumption during idle time is essential to promoting low power consumption in small information devices.
As a result, Japanese Unexamined Patent Appl. Pub. JP-A-2010-036528 teaches technology that intermittently turns a sensor on and off to suppress current consumption by the sensor.
In addition, when an SoC is used as the controller, devices that change the operating mode to a sleep mode to minimize the functionality of the microprocessor that functions as the main control unit inside the SoC when a non-operating idle state that is entered to reduce power consumption continues for a specified time are also known.
However, when the controller enters the sleep mode, the power supply for driving the user interface and sensors for monitoring the operating state cannot be stopped.
When a SoC according to the related art uses a photosensor for status monitoring, the detection timing cannot be managed if the controller is set to the sleep mode. The sleep mode can therefore not be entered when the photosensor must be driven intermittently and detection performed. The problem with a controller that can enter a sleep mode is that the sleep mode cannot be enabled, the controller must always remain in the drive state, and energy cannot be conserved. In addition, the controller does not need to monitor sensor output until the sensor stabilizes, but the sleep mode is not enabled during this time.